---------------------------------------------------------- Engines-List Digest Archive --- Total Messages Posted Tue 10/16/07: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:38 AM - Re: Re: Ring flutter? (AzevedoFlyer@aol.com) 2. 07:23 AM - Re: Knock sensors? (Noel Loveys) 3. 08:06 AM - Re: Knock sensors? (Hinde, Frank George (Corvallis)) 4. 08:21 AM - Re: Knock sensors? (Monty Barrett Sr) 5. 08:53 AM - Re: Re: Ring flutter? (Monty Barrett Sr) 6. 04:51 PM - Re: Knock sensors? (lessdragprod@aol.com) ________________________________ Message 1 _____________________________________ Time: 01:38:20 AM PST US From: AzevedoFlyer@aol.com Subject: Re: Engines-List: Re: Ring flutter? Gary, Baring gross factors like excessively worn groove or mismatched axial clearance between ring and groove, ring flutter results from inertial forces + pressure unbalance between the top face and lower face of the ring. Mostly, it restricts itself to the first compression ring but I've seen the 2nd and occasionally even the 3rd (oil ring) undergoing flutter. For this unbalancing to occur, some gas has to leak into and pressurize the inter ring (1st - 2nd) cavity. Along the expansion stroke, this stagnation pressure becomes higher than the pressure acting over the top of the 1st ring. When this occurs, the 1st ring lifts from its lower face contact with the groove. How flutter progresses from this point onwards can become a very complex process. On the other hand, if you ran an engine without any load on it at high revs, inertia will become predominant and lift the 1st ring, causing flutter. In a plane, such a situation might conceivably occur if you dive with throttle closed and the propeller drives the engine to a sufficiently high revs. Lastly, flutter refers to a rapid oscillation of the ring in the groove. Not to a normal change of lateral face contact of the ring with the groove. This last is usually precluded by either ring geometry (torsion) or by adhesive forces generated by oil surface tension. Cheers, Miguel N8714D PA22/20-150 ________________________________ Message 2 _____________________________________ Time: 07:23:44 AM PST US From: "Noel Loveys" Subject: RE: Engines-List: Knock sensors? Thanks... I had heard of LOP before long enough ago to have completely forgotten. When in technical school we were always told to lean ROP Noel > -----Original Message----- > From: owner-engines-list-server@matronics.com > [mailto:owner-engines-list-server@matronics.com] On Behalf Of > Greg Young > Sent: Monday, October 15, 2007 7:35 PM > To: engines-list@matronics.com > Subject: RE: Engines-List: Knock sensors? > > > > LOP=lean of peak, ROP=rich of peak > > Regards, > Greg Young > > > > -----Original Message----- > > From: owner-engines-list-server@matronics.com > > [mailto:owner-engines-list-server@matronics.com] On Behalf Of > > Noel Loveys > > Sent: Monday, October 15, 2007 8:43 AM > > To: engines-list@matronics.com > > Subject: RE: Engines-List: Knock sensors? > > > > > > > > I've seen the term LOP used a few times..... But have no idea > > what it means. > > > > Noel > > > > > > ________________________________ Message 3 _____________________________________ Time: 08:06:09 AM PST US Subject: RE: Engines-List: Knock sensors? From: "Hinde, Frank George (Corvallis)" LOP is the most efficient place to run the motor. From my reading of the Lycoming power chart it has about a 10% reduction in the BSFC in LOP vs ROP (BSFC =.45 at 50F LOP and .5 at 80F ROP). Rumour has it that the only way the old Howard Hughes Connies made it across the Atlantic was to run the motors LOP. Its about the only place I run my motor apart from take off and landing. Frank RV7a TMX IO360 -----Original Message----- From: owner-engines-list-server@matronics.com [mailto:owner-engines-list-server@matronics.com] On Behalf Of Noel Loveys Sent: Tuesday, October 16, 2007 7:22 AM Subject: RE: Engines-List: Knock sensors? Thanks... I had heard of LOP before long enough ago to have completely forgotten. When in technical school we were always told to lean ROP Noel ________________________________ Message 4 _____________________________________ Time: 08:21:37 AM PST US Subject: RE: Engines-List: Knock sensors? From: "Monty Barrett Sr" The Wright 3350 engines in Super Connies and also the B-29 were operated LOP. The FE had the most important job on the flight crew. As I remember, The FE also had a set of throttles. Monty Barrett -----Original Message----- From: owner-engines-list-server@matronics.com [mailto:owner-engines-list-server@matronics.com] On Behalf Of Hinde, Frank George (Corvallis) Sent: Tuesday, October 16, 2007 9:04 AM Subject: RE: Engines-List: Knock sensors? LOP is the most efficient place to run the motor. From my reading of the Lycoming power chart it has about a 10% reduction in the BSFC in LOP vs ROP (BSFC =.45 at 50F LOP and .5 at 80F ROP). Rumour has it that the only way the old Howard Hughes Connies made it across the Atlantic was to run the motors LOP. Its about the only place I run my motor apart from take off and landing. Frank RV7a TMX IO360 -----Original Message----- From: owner-engines-list-server@matronics.com [mailto:owner-engines-list-server@matronics.com] On Behalf Of Noel Loveys Sent: Tuesday, October 16, 2007 7:22 AM Subject: RE: Engines-List: Knock sensors? Thanks... I had heard of LOP before long enough ago to have completely forgotten. When in technical school we were always told to lean ROP Noel ________________________________ Message 5 _____________________________________ Time: 08:53:45 AM PST US Subject: RE: Engines-List: Re: Ring flutter? From: "Monty Barrett Sr" In many years of aircraft ( and other engines, some of which are very high speed ), I don't think I have ever encountered a positive ring flutter situation. The ring damage I have seen other than excessive groove clearance has been caused by not enough end gap, high power being used before cylinders were up to the proper temperature, ( 300 F ) and detonation. An interesting observation is that a large percentage of new piston rings are NOT FLAT, but have a wavy surface. A couple of manufactures' go to great lengths to insure the surfaces a absolutely flat. They use very sophisticated equipment to inspect for this condition. Pressure is always present behind the rings during the compression, power strokes and even thru the blowdown period of exhaust. Pressure is what makes the ring seal. I agree that the pressure behind the 2nd ring is not as high as the top ring. High engine speed, high forward speed and low manifold pressure is more likely to damage counterweights on the crank; that is the big danger with operating an engine in this manner. Also dangerous is the fact that the cylinder barrel and head will cool at a much faster rate with the above mentioned operating procedure than the piston, which leads to the barrel shrinking down on the piston. I have seen piston top lands with metal " pulled " . This phenomenon is usually referred to as " shock cooling ". The current design piston rings are semi-keystone ( half wedge ) which are designed to move in and out radially so not to " stick " in the groove and to help the ring seal when the cylinder is NOT up to temperature. Older designs were full keystone. Some engines still use full keystone rings. Some piston rings also have an angle cut on the inboard edge to allow some " twisting " of the ring and is used for a couple of purposes; 1. to place a sharp corner of the ring to the barrel face for oil scavenging, 2. to reduce barrel wear because the tension of the ring is somewhat reduced when the ring is " twisted ", 3. to allow the ring to " hydroplane " over an oil film. Plasma filled rings are rarely twisted. In fact, a plasma filled ring should be installed with great care so as NOT to twist the ring. Monty Barrett -----Original Message----- From: owner-engines-list-server@matronics.com [mailto:owner-engines-list-server@matronics.com] On Behalf Of AzevedoFlyer@aol.com Sent: Saturday, October 13, 2007 7:00 PM Subject: Re: Engines-List: Re: Ring flutter? Gary, Baring gross factors like excessively worn groove or mismatched axial clearance between ring and groove, ring flutter results from inertial forces + pressure unbalance between the top face and lower face of the ring. Mostly, it restricts itself to the first compression ring but I've seen the 2nd and occasionally even the 3rd (oil ring) undergoing flutter. For this unbalancing to occur, some gas has to leak into and pressurize the inter ring (1st - 2nd) cavity. Along the expansion stroke, this stagnation pressure becomes higher than the pressure acting over the top of the 1st ring. When this occurs, the 1st ring lifts from its lower face contact with the groove. How flutter progresses from this point onwards can become a very complex process. On the other hand, if you ran an engine without any load on it at high revs, inertia will become predominant and lift the 1st ring, causing flutter. In a plane, such a situation might conceivably occur if you dive with throttle closed and the propeller drives the engine to a sufficiently high revs. Lastly, flutter refers to a rapid oscillation of the ring in the groove. Not to a normal change of lateral face contact of the ring with the groove. This last is usually precluded by either ring geometry (torsion) or by adhesive forces generated by oil surface tension. Cheers, Miguel N8714D PA22/20-150 ________________________________ See ________________________________ Message 6 _____________________________________ Time: 04:51:25 PM PST US Subject: Re: Engines-List: Knock sensors? From: lessdragprod@aol.com I talked with one of the local pilots who was a flight engineer on the Connies.? They not only operated the engine LOP, they increase the manifold pressure to recover the power lost by operating LOP. As Don described it, the sequence went like this to set the cruise power mixture and power setting.? (They used a power gauge.) When they leveled out at cruise altitude, the power gauge?showed a number with the initially rich mixture setting.? They would calculate?a reduced?power setting?by subtracting 10% or 15% (depending on the supercharger blower being in high or low blower) from the original power setting. They would lean the mixture.? As the mixture is leaned, the power gauge would show an?increase in power, and then show a?decrease in power. When they got to the lower?calculated power setting, they had the mixture set. Now they increased the manifold pressure until they reached the original power setting. Sounds simple.? Just do this smoothly on four engines at the same?time.? :-) For our normally aspirated engines, the capability of obtaining the power recovery isn't there. I suspect the same power reduction and fuel fow reduction could be done running Best Economy and reducing the manifold pressure.? Someone interested in doing a test program? Regards, Jim Ayers -----Original Message----- From: Monty Barrett Sr Sent: Tue, 16 Oct 2007 8:25 am Subject: RE: Engines-List: Knock sensors? The Wright 3350 engines in Super Connies and also the B-29 were operated LOP. The FE had the most important job on the flight crew. As I remember, The FE also had a set of throttles. Monty Barrett -----Original Message----- From: owner-engines-list-server@matronics.com [mailto:owner-engines-list-server@matronics.com] On Behalf Of Hinde, Frank George (Corvallis) Sent: Tuesday, October 16, 2007 9:04 AM Subject: RE: Engines-List: Knock sensors? LOP is the most efficient place to run the motor. From my reading of the Lycoming power chart it has about a 10% reduction in the BSFC in LOP vs ROP (BSFC =.45 at 50F LOP and .5 at 80F ROP). Rumour has it that the only way the old Howard Hughes Connies made it across the Atlantic was to run the motors LOP. Its about the only place I run my motor apart from take off and landing. Frank RV7a TMX IO360 -----Original Message----- From: owner-engines-list-server@matronics.com [mailto:owner-engines-list-server@matronics.com] On Behalf Of Noel Loveys Sent: Tuesday, October 16, 2007 7:22 AM Subject: RE: Engines-List: Knock sensors? Thanks... I had heard of LOP before long enough ago to have completely forgotten. When in technical school we were always told to lean ROP Noel ________________________________________________________________________ Email and AIM finally together. 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